1. Field of the Invention
This invention relates to a fire alarm system in which terminal units, such as fire detectors and smoke blocking and exhausting units, are connected to a receiver thereof.
2. Description of the Related Art
As a conventional fire alarm system, a P-connection fire alarm system has been known in which a multiplicity terminal units are connected to a receiver thereof in such a manner that each terminal unit is enabled to communicate with the receiver by an individual signal. However, the foregoing conventional fire alarm system cannot preferably be adapted to a large size system because the number of signal lines increases in proportion to the number of the terminal units.
Accordingly, an R-connection fire alarm system has been suggested in which an individual address is given to each terminal unit and thus the receiver is allowed to communicate with each terminal unit through the address. As a result, the number of the signal lines can be decreased significantly.
However, the R-connection fire alarm system must comprise a relay in a case where units to be controlled, such as smoke blocking and exhausting units, are disposed, in order to decode commands issued from the receiver and instruct the unit to be operated. In a small size fire alarm system in which a large number of terminal units are not disposed, there arises a problem in that a space for disposing the relay cannot be provided because the space given to the fire alarm system is not sufficiently large.